The adjustment of the pitch angle of certain stator blades in a turbomachine is intended to optimize the efficiency of this turbomachine and to reduce its fuel consumption in the various flight configurations. This adjustment is generally carried out, for one or more rows of blades, by means of a control annulus which externally surrounds the stator of the turbomachine and which is rotatable about the longitudinal axis of the stator by a drive means such as a ram or an electric motor. The rotation of the annulus is transmitted by control levers of the linkage type to the blades of the row, each control lever being secured to a blade at one of its ends and carrying at its other end a peg which is engaged in a cylindrical housing of the control annulus.
The peg is mounted in an orifice of the end of the lever and is fixed to the lever by crimping, this operation consisting in squashing the end of the peg onto the end of the lever which rests on an annular flange of the peg. This operation engenders significant stresses in that part of the lever on which the crimping of the peg is carried out, thus making this part of the lever more fragile.
When adjusting the pitch angle of the blades, the control lever is subjected to bending forces at its end carrying the peg and the peg is subjected to torsional forces.
The mechanical strength of the lever being decreased by the crimping of the peg, cracks or fissures may appear on the lever after a certain operating time of the turbomachine and cause the breakage of the control lever, which may provoke the shutdown of the turbomachine and must therefore be regarded as a very serious incident.